The present invention is an ignition control apparatus for an internal combustion engine. More importantly, the invention utilizes the characteristics of a high voltage MOSFET device to control the operation of the ignition system at voltages not previously possible with conventional contactless (electronic) ignition systems. Accordingly, the present invention further enables the elimination, or substantial cost reduction, of components found in conventional ignition systems.
Internal combustion engine ignition systems have commonly used ignition coils powered by a low voltage, such as a 12 volt car battery. The considerably higher voltage potential required to fire a spark plug, and thus initiate combustion, is generated in a coil and distributed to the spark plugs by a spinning rotor in the distributor.
In high performance motor applications, the voltage potential needed to assure complete combustion of the air-fuel mixture is much higher than that provided by a normal ignition system. In order to over,come this problem, high voltage coils were developed, where an increased number of windings produced the increased potential but resulted in slower response times than the "normal use" ignition coils. A further complication occurs in trying to distribute the higher voltage--the mechanical contacts of the distributor and rotor are subjected to higher wear rates, necessitating more frequent replacement.
More recently, electronic ignition systems employing capacitive discharge devices and multiple coils have emerged. Frequently, the distributor has been replaced by computer modules, and the firing of the spark plugs is actually controlled by a transistor that switches the low voltage applied to the primary coil of a step-up type transformer.
Heretofore, a number of patents have disclosed ignition control devices for internal combustion engines, the relevant portions of which are hereby incorporated by reference and may be briefly summarized as follows:
U.S. Pat. No. 4,597,366 to Chart, issued Jul. 1, 1986, discloses an apparatus for distributing a high voltage arc from the high voltage ignition coil of a piston type internal combustion engine to the respective spark plug terminals by means of a high resistance, field-interrupting dielectric device which has an aperture therethrough defining a conductive path through the non-conductive dielectric device.
U.S. Pat. No. 4,175,506 to Sakamoto et al., issued Nov. 27, 1979, teaches an electric ignition control system for an internal combustion engine having a first pulse generator for producing pulses at each 180.degree. interval of crank shaft revolution, a second pulse generator for delivering a predetermined number of pulses, such as 1800 counts, during each 180.degree. interval, and a read only memory for producing a digital signal representing ignition timing in response to both engine speed and throttle opening. When the first counter circuit has counted the number of the second pulse generator pulses equal to the value of the digital signal from the memory, the primary current of an ignition coil applied from a battery to the primary coil thereof is interrupted for producing a high voltage to establish an ignition spark across the gap of a spark plug.
U.S. Pat. No. 4,130,097 to Ford, issued Dec. 19, 1978, discloses a closed loop electronic ignition system for internal combustion engines, in which a comparison is made between a first and a second signal to maintain coincidence between the signals, so that the second stage of combustion always occurs at a fixed predetermined crank angle, irrespective of the speed and load on the engine, as well as all other parameters which can affect ignition timing. U.S. Pat. No. 4,130,096, also to Ford, issued Dec. 19, 1978, teaches a similar closed loop electronic ignition system where if non-coincidence is detected between the two signals, the ignition timing is either advanced or retarded so as to maintain coincidence between the signals.
U.S. Pat. No. 4,109,630 to Richeson, Jr. et. al., issued Aug. 29, 1978, discloses an electronic ignition system for an internal combustion engine having a timing signal source comprising an oscillator for providing a carrier signal; an electronic network connected to the oscillator; and a detector for demodulating a modulated carrier signal and providing an output signal indicative of a predetermined rotational position of the engine. The output signal is supplied to switching circuitry for switching the primary of an ignition coil and providing a high voltage output pulse at a time synchronized with said predetermined rotational position of the engine.
U.S. Pat. No. 4,918,389 to Schleupen et. al., issued Apr. 17, 1990, teaches the detection of misfiring in internal combustion engines by detecting the voltage induced in the primary winding of the ignition coil, and comparing it to reference voltage which represents normal firing.
Of particular relevance are those ignition devices for internal combustion engines that employ transistor components therein, for example:
U.S. Pat. No. 5,113,815 to Ikeda, issued May 19, 1992, discloses an ignition control apparatus for an internal combustion engine in which the engine can not be started without the operation of a switch unit which may further include a control element in the form of a resistor or a transistor.
U.S. Pat. No. 5,050,573 to Meinders et. al., issued Sep. 24, 1991, teaches an ignition device for an internal combustion engine Including a preselector stage and an output stage for controlling the flow of current through the primary winding of an ignition transformer. The ignition device is particularly suited for an externally ignited internal combustion engine. The output stage comprises a pnp-transistor having its collector terminal directly coupled to a ground connection of the ignition device to improve proper loss dissipation. A decoupling device is coupled between the preselector stage and the output stage, and is provided to protect the preselector stage by decoupling it from the output stage.
U.S. Pat. No. 4,397,290 to Tanaka et. al., issued Aug. 9, 1983, discloses a supply-voltage-compensated contactless ignition system for internal combustion engines that includes an input transistor operable in response to an engine ignition signal so as to control the operation of a power transistor to control the energization of an ignition coil; with the operating level of the input transistors being varied with variation in the supply voltage. The system further includes a current mirror circuit having first and second current shunt paths including first and second transistors which are connected in parallel with a voltage clamping device such that the each current path shunts a current increased over that of the other in response to a rise of the supply voltage beyond a predetermined value.
U.S. Pat. No. 4,343,285 to Brammer et. al., issued Aug. 10, 1982, teaches a Hall generator integrated circuit in a transistor-controlled ignition system of an internal combustion engine and an integrated circuit board which carries the circuit elements for overvoltage protection, amplification, and the power output stage mounted together in one building block. Preferably, the conductive element and the permanent magnet of the Hall generator are also integrated into the building block as is a pressure sensor. The output of the pressure sensor is directly applied to the circuits in the printed circuit board. The unit occupies little space and eliminates the need for external leads interconnecting the ignition coil and the output circuit.
In accordance with the present invention, there is provided a contactless ignition apparatus for an internal combustion engine, comprising:
a high voltage DC power source for supplying direct current at a first potential; PA1 an ignition transformer including a core, a primary coil associated with the core and connected to said high voltage DC power source to receive the direct current at a first potential therefrom and a secondary coil, also associated with the core, and adapted to produce a DC voltage of a second potential, greater than the first potential, in response to the application of the direct current at a first potential to the primary coil; PA1 a spark plug, connected to the secondary coil of said ignition transformer, for generating a spark to ignite an air-fuel mixture in the internal combustion engine in response to the DE voltage of the second potential; PA1 a high voltage transistor, connected in series with said high voltage DC power source and the primary coil of said ignition transformer, for controlling the passage of the direct current of the first potential through the primary coil of said ignition transformer in response to a logic signal applied thereto; and PA1 an ignition control module, connected to said high voltage transistor, for generating a low voltage logic signal to control the passage of the direct current of the first potential through the primary coil of said ignition transformer so as to control ignition of said spark plug. PA1 a high voltage DC power source for supplying a DC voltage of at least 1000 volts; PA1 an ignition transformer for producing a stepped-up DC voltage of at least 20,000 volts in response to the DC voltage, the stepped-up DC voltage being suitable to drive an ignition device; PA1 a high voltage transistor, connected in series with said high voltage DC power source and said ignition transformer, to control the application of the DC voltage to said ignition transformer in response to a logic signal applied thereto; and PA1 an ignition control module, electrically connected to said high voltage transistor, for generating the logic signal to control the high voltage transistor and thereby the application of the DC voltage to said ignition transformer.
In accordance with another aspect of the present invention, there is provided a contactless ignition apparatus, comprising:
One aspect of the present invention is based on the observation of problems with conventional ignition systems, where components therein are subject to wear, or are necessarily complex and expensive in order to handle the very high voltages needed to drive spark plugs or equivalent ignition devices. This aspect is based on the discovery of the use of high voltage MOSFETs to switch high voltages and thus alleviate these problems. Use of high voltage MOSFETs enables switching of higher primary voltages, by an ignition computer or control module, thereby eliminating the need for contact switching components, and/or reducing the ignition coil sizes.
This technique can be implemented, for example, by employing a high voltage MOSFET to control the firing of one or more spark plugs in an internal combustion ignition system. Furthermore, an ignition control apparatus implementing the invention may include spark plugs wherein a small secondary coil is integrated into the spark plug package or the high voltage distribution circuitry itself. The technique described is advantageous because it improves reliability and performance, while decreasing the complexity and cost, of electronic ignition systems for internal combustion engines.